Multipolar dynamo-electric machine.



B. A.- BEHREND.

MULTIPOLAB. DYNAMO ELECTRIC mcnmn. APPLICATION FILED 8321316, 1905.

1,071,546 Patented Aug.26, 1913.

2 SHEETS-SHEET 1.

Inventor:

pjittorng.

B. AJBBHRBND.

MULTIPOLAR DYNAMO ELECTRIC MACHINE.

AYPLIOATIOK FILED 8112116, 1905.

- 1,071,546. Patented Aug.26, 1913. 2 sums-sum 2.

frzm srztor m tnesses flern ardArl/l 10' .Be/zremi lttorney.

' UNITED STATES PATENT OFFICE;

BERNARD ARTHUR BEHBEND, OF NOBWOOD, OHIO, ASSIGNOB TO ALLIS-CHALMERS COMPANY, A CORPORATION OF NEW JERSEY, AND THE BULLOCK ELECTRIC MANU- FACTURING COMPANY, A CORPORATION OF OHIO.

MULTIPOLAR DYNAMO-ELECTRIC MACHINE.

Specification of Letters Patent.

Patented Aug.-26, 1913.

Application filed September 16, 1905. Serial No. 278,807.

To all whom it may concern:

Be it known that I, BERNARD A. Bmmnno, citizen of the United States, residing at Norwood, in the county of Hamilton and State of Ohio, have invented certain new and useful Improvements in Multipolar Dy- In largejdynamo electric machines of the multipolar type, current is led to and .from t e armature by a "plurality of groups of positive :and' negative brushes,

arranged around the conunutatorr In a common type of .machine each group of, brushes is supported by a brush {holder frame comprising a p gra brushes together and all the grou tive brushes together by means 0 two rings of strap copper, one ring being connected to the positive brushes and the positive lead. connected to .the'

and the other ring bein negative brushes" and t e negativev lead. Heretofore these two rings have beenusually arranged adjacent each other and have been connected to either the inner or outer ends ofthe bolts or rods which support the brush holder frames. The terms inner and outer are used here and elsewhere in this specification as convenient terms to denote respectively parts'nearer to and farther from the frame of the machine. It has been found when the two connecting rings are both joined to either the inner or outer ends of the bolts, that the current is not equally distributed through the brushes of each group, but the brushes nearer the connecting rings carry more current than the brushes more remote from the connecting rings, the amounts of current carried by the brushes of each group gradually decreasing from the brush nearest the connecting ring to the brush on the opposite end of the stud. Thus one or more of the brushes of each means-to opposite ends of the alternately i stud and two arms, which arms are pivoted to bolts of rods orted on but insulated from arms intewith the largebrush yoke. Itisicustomary to connect all the groups of positive sot negaagroup are freqluently overloaded, which overloading resu ts in considerable sparking and heating of the adjacent portion of the commutator. The result is that the stress in the commutator bars due to heat expansion is unequally distributed. One portion expands at a greater rate than the other with a result that the commutator is twisted or distorted.

Now the object of my invention is to avoid this unequal heating efi'ect by distributing the current equally over the commutator.

In carrying out my invention I arrange the positive and negative brush connecting ositive and negative brush studs respectivel in consequence of whichlboth ends of the commutawe will beheated substantially equally.

of the-multipolar type having a plurality of alternatelyiarranged groups of positive and negative brushes mounted. in brush holders supported on 'brushholder frames, and separateconnectingmeansior the positive and negative brushes, the twoconnecting means being"connected" to opposite sides of the brush holder frames, vwhereby there will be ,.moreequ'al"distribution of current over the commutator and both ends of the latter will be uniformly heated."

Referring to the drawings, which embody one form of the invention, Figure l is an elevation of a portion of a dynamo electric machine having my invention applied thereto';.Fig..2 is a lan of the same; Fig. 3 is a development c the winding and commutator of an eight-pole machine showing the brushes and the relative arrangements of the positive and negative cross connectors or connecting rings, and Fig. 4 is a sectional view taken approximately on the line 4-4 of Fig. 1.

I have shown at 10 a portion of the field frame of a dynamo electric machine surrounding the armature 11 which is mounted on the shaft 12. Mounted in rollers, one of which shown at 13, is the large adjustable brush supporting ring or yoke 14. Extendhrulh yoke are the arms 15 in "cured the horizontal rods or voted to and insulated from the the frames comprising the arms brush holder studs 18. Mount- More specifically, considered, my invention co'nsists of a'dynamo electric machine ed upon the studs are the brush holders, 19

and brush supporting members so far described is old and I claim no novelty therein.

The cross connecting rings are shown at 22 and 23 respectively. These rings are arranged at opposite ends of the commutator, instead of being arranged at the same end as is customary. Alternate groups of brushes are connected to the rings 22 and 23 by means of one or the other of the pair of arms 17 and the straps 24, which connect the rings respectively to opposite ends of alternate bolts 16. In Fig. 3 the positive main is shown connected to the outer ring 22 and the positive brushes, and the negative main connected to the inner ring 23 and the negative brushes, though if desired the positive main may be connected to the inner ring 23 and the negative main to the outer ring 22.

The proportions of current carried by the several brushes of each group has been found in practice to depend on the relative distances from the brushes to the cross connecting ring to which the group is connected. For example the outer brush of each group connected to the outer ring carries the greatest amount of current, and the inner brush of the same group carries the least amount, the amounts gradually decreasing from the outer brush to t-heinner brush. This unequal distribution of current is probably due, to a great extent, to the fact that the electrical resistance between the brushes and their associated cross-connecting ring is least for the brushes nearest the ring and gradually increases to thebrushes most remote from the ring. Consequently, for the groups of brushes connected to the outer ring, the sparking and the current density at the commutator surface are greatest under the outer brushes and least under the inner brushes, and the outer end of the commutator surface is heated more than is the inner end thereof. On the other hand, for the groups of brushes connected to the inner ring, the sparking and the current density at the commutator surface are greatest under the inner brushes and least under the outer brushes and the inner end of the commutator surface is heated more than is the outer end thereof. Therefore, the average sparking and the average current density at the surface of the commutator is substantially equal at both ends thereof, and substantially uniform throughout the length thereof, and the commutator is heated substantially-equally throughout. There is thus less tendenc for the commutator bars to twist and to ome displaced. A further advantage gained by this arrangement is that there are fewer strains to be guarded against, and consequently less labor and material are required in the construction of the commutator.

VVhat' I claim as new and desire to secure by Letters Iatent is:

1. In a dynamo electric machine, a-commutator, positive brush means extending along the length of said commutator and negative brush means similarly extending, a terminal connected to the outer end of the brush means of one polarity and a terminal connected to the inner end of the brush means of opposite polarity.

2. In a dynamo electric machine, a commutator, a group of positive electrically connected brushes extending along. the' length of said commutator, a group of negative electrically connected brushes extending along the length of said commutator, a terminal connected to the outer end of said group of brushes of one olarity and a terminal connected to the inner end of said group of brushes of opposite polarity.

carrying means for the one set of groups, and a cross connector connected to the inner ends of said brush carrying means for the other set of groups.

In testimony whereof I atfix my signature, in the presence of two witnesses.

BERNARD ARTHUR BEHKEND. Witnesses:

RUBY ROBINSON, ARTHUR F. Kwrs. 

